[klh]

Rick,

Have you seen the center channel being built to match the GR Research Alpha-LS speaker? I don't mean to mention a competitor's speaker on your forumn other than to ask you what you think of the merits of that design and whether you've thought of or would consider designing a center channel based on similar principles? It seems to me that a line source in that configuration defies or doesn't take advantage of a lot of the theory in Dr Griffin's white paper (and is thus flawwed). Am I correct? As they say, the proof is in the pudding, so listening to the speaker will reveal the ultimate answer, but I'm just talking theory. Obviously a vertical line source with a sound transparent screen in front would be best for those who want to have a multifunctional audio/video setup, but that's not practical for many people.  Have you worked on (or have plans to work on) an alternative to a horizontal MTM (or similar) design?

Thanks,

Krister

[Jim Griffin]

Krister,

I have sampled the thread on the possible center channel for the Alphas.  While I live in Tennessee, I'm from Missouri (the Show Me State) on that design as I have reservations of its effectiveness.  We will hear if they are successful.

To me the best center channel with a set of line arrays as the left and right front speakers is to have a phantom center--no center speaker.  I say that because of the wider imaging of the line array speakers vs. conventional point source speakers.  Line arrays when operated in their near field have a 3 dB per distance doubling sound fall off (vs. the 6 dB per distance doubling for the usual point sources), so you will find that both the front to back and left to right sound falloff in the listening room will be less than for point source speakers.  

Bottom line to me is that unless you have your line arrays spaced very far apart, you will find that the center fill will be there without the need for a center channel speaker.  I would suggest that you try it without a center channel and see how you like the results.  All surround sound processors and DVD players have the option to be set-up for no center channel.

The other factor to consider with line arrays as the fronts and point source speakers for the center channel and surround speakers is the  difference in sound fall-off between the two different type of sources.  This can be set-up for very limited seating in the room but you will have a minimal sweet spot.  But, what if you want a really awesome system?  Why not a set of line arrays for the left and right rears to go with the front arrays?  Now you would have a huge sweet spot--virtually the entire room would be in the image area.  Now that would be cool and a sufficient improvement over a mixed line and point source speakers system.

Jim

[Rick Craig]

Rick,

Have you seen the center channel being built to match the GR Research Alpha-LS speaker? I don't mean to mention a competitor's speaker on your forumn other than to ask you what you think of the merits of that design and whether you've thought of or would consider designing a center channel based on similar principles? It seems to me that a line source in that configuration defies or doesn't take advantage of a lot of the theory in Dr Griffin's white paper (and is thus flawwed). Am I correct? As the ...

Yes, I've seen that. No comment from me other than you won't be seeing me design anything like that. I've actually designed several center channels, all in the WMTW format. This gives you wide and uniform coverage. If you look at the high end speaker companies that are well-respected they all use that format for their best HT systems.

I tend to agree with Jim in that a phantom center is best. For those of us with extensive line array listening experience I think most would agree. The center fill from a good array with flat off-axis response is excellent. If used in an array the planar drivers that have limited off-axis response *may* benefit from the center fill of a dedicated CC.

If you do use a center channel a matching line array is best but as you noted for many people that's not practical. At some point I plan to experiment with mixing  point source CC's and a pair of arrays.

[klh]

All very valid points, and I respect both of your opinions on the lack of a need for a center channel. The main worry is obviously off axis response in a living room/theater type setting; at times people are bound to sit outside the front right or left speaker. It makes sense to use the phantom mode and see how it sounds in practical everyday life... if a center channel needed, then you know for sure. I would imagine that if one uses a WMTW center, then the gain would have to be increased a bit for a given (or average) listening distance, but that's not hard to do. A WMTW design may not be ideal, but if it sound is reasonablly close (which would be expected since essentially the same drivers are used), that may be all one can expect. Besides, exact uniformity of sound for home theater isn't as necessary as for serious music listening... and when doing serious music listening one would want to to be in the sweet spot and most likely listen in phantom mode anyway.

[Rick Craig]

All very valid points, and I respect both of your opinions on the lack of a need for a center channel. The main worry is obviously off axis response in a living room/theater type setting; at times people are bound to sit outside the front right or left speaker. It makes sense to use the phantom mode and see how it sounds in practical everyday life... if a center channel needed, then you know for sure. I would imagine that if one uses a WMTW center, then the gain would have to be increased a bit for a given  ...

I do have an idea for a compact center channel using the same drivers from my arrays but in a different configuration (not a WMTW). I'm going to see how well it works in my system on both HT and 5.1 SACD/DVD-A.

[JoshK]

I haven't heard a true line array before, but even with my RM40's I wouldn't ever want to use a center channel, and the one time I heard the RM/X's I'd conclude that I wouldn't use one with them either.  

I get really good centralized vocal presentation with TV, movies etc without the use of a center.  I personally think the center was invented more for the mass consumer who's setup is lacking and thereby adds value to use a center.

[Rick Craig]

I haven't heard a true line array before, but even with my RM40's I wouldn't ever want to use a center channel, and the one time I heard the RM/X's I'd conclude that I wouldn't use one with them either.  

I get really good centralized vocal presentation with TV, movies etc without the use of a center.  I personally think the center was invented more for the mass consumer who's setup is lacking and thereby adds value to use a center.

It really depends on the source and how the audio was mixed by the sound engineer. The center channel evolved from mixing for movie theaters where it helps "center" the dialogue and improves audience coverage by filling in where the L/R horn-based systems lose coverage.

With the multi-channel SACD/DVD-A formats the center becomes more important. The idea here is to use the CC for discrete sounds to create a multi-dimensional soundstage. Some recordings don't use it in that way but mix in a little of the L/R signals to create an arc in front of the listener. This is effective for string quartets, vocal ensembles, small jazz combos,etc. to make the sound more realistic.